Refrigerant control means



P 1959 E. w.- ZEARFOSS, JR 2,901,894

REFRIGERANT CONTROL MEANS Filed March 10, 1955 2 Sheets-Sheet 1 9 u: O N

P Q N i L i :0 1k

INVENTOR.

ELMER W. ZEARFOSS Jr.

ATTORNEY p 1959 E. w. ZEARFOSS, JR 2,901,894

REFRIGERANT CONTROL MEANS Filed March 10, 1955 2 Sheets-Sheet 2 ATTORNEYUnited States Patent REFRIGERANT CONTROL MEANS Elmer w. Zearfoss, In,Philadelphia, Pa.

Application March 10, 1955, Serial No. 493,316

1 Claim. (Cl. 62-509) My invention relates to a refrigerating apparatusof the type in which. acapillary tube is employed as the pressurereducing means between the high and low sides of the apparatus.

Qne object of the invention is to produce an improved refrigeratingapparatus of the type set forth.

Under theoretically ideal, controlled operating conditions and given aconstant refrigeration load, it is pos sible to design a system in whichall components are balanced and in which the flow of refrigerant throughthe evaporator is at optimum so that a high degree of efficiency isattained.

But, in practice, the refrigeration load and the temperature-pressureconditions which affect the balance of the system, vary and thus createproblems in design and in control.

To solve this problem, it has heretofore been proposed to provide anevaporator circuit having a refrigerant storage capacity such as tosuflice for maximum requirements. This expedient is not altogetherdesirable in a flooded type system because the practicableconfigurations of the evaporator are limited and because a relativelyhigh refrigerant charge is required. In the dry, or accumulator type ofsystem, the expedient referred to is not desirable because it willresult in undesirable peak load and onset cycle performance whichreflect improper refrigerant distribution and flow control.

Furthermore, the inclusion of an accumulator in the system creates oillogging problems.

It is therefore a further object of the invention to produce a system inwhich all of the foregoing problems are overcome.

More specifically, the object of the invention is to produce a whollyself-regulating refrigerating apparatus in which the amount ofrefrigerant which reaches the evaporator is automatically regulated bythe demand imposed on the evaporator to the end that the evaporatorwill, at all times, receive a supply of refrigerant which is, in effect,a function of the temperature of the spent refrigerant gas leaving theevaporator.

A still further object is to produce an improved refrigerating apparatusin which the regulation of the supply of liquid refrigerant reaching theevaporator is effected without any moving parts and in a manner whichdoes not appreciably increase the cost or weight of the apparatus andwhich involves no maintainance cost whatever.

In mose types of apparatus involving the use of a capillary tube it isnecessarythat'therefrigerant charge introduced into the sealed circuitbe accurately or, at least, very closely estimated. Otherwise, for wellknown reasons, satisfactory and eflicient operation may becomeimpossible.

It is therefore a still further object of the invention to produce animproved refrigerating apparatus in which the volume of the refrigerantcharge initially introduced into the system is not so critical and neednot be accurately predetermined.

ice

In all refrigerating machines, over-rides or extremes of temperature, bethey on the cold or on the warm side are not desirable. In other words,uniform operation, within predetermined limits is desirable and, to thatend, the cycling of the apparatus should be such as uniformly tomaintain the desired temperature.

It is therefore a still further object of the invention to produce animproved refrigerating apparatus which has a cycling performance Withouthunting and undue over-ride.

These and other'objects are attained by my invention asset forth in thefollowing specification and as shown in the accompanying drawings inwhich:

Fig. 1 is a diagrammatic view showing one embodiment of the invention.

Fig. 2 is a similar view showing a secondembodiment of the invention.

Referring to Fig. 1, 10 is a compressor, 12'is a condenser and 14 is acapillary tube for conducting the condensed refrigerant to theevaporator. These parts are conventional in structure and in operationand therefore need not be shown nor described in detail.

According to my invention, capillary 14 communicates at 18, with a pipe19 for conducting refrigerant to the intake end 20 of an evaporator 22with, or without the interposition of a restrictor 24. Capillary tube 14also communicates at 18, with a pipe 25 for conducting refrigerant to ablind accumulator 26. It will be noted that the discharge end ofcapillary 14 (i.e. point 18) is above at least a substantial portion ofaccumulator 26. Pipe 25 enters the accumulator at its lower end andextends upwardly to form a riser tube 27 which terminates in: the upperportion of the accumulator 26. Riser tube 27 is provided with a measuredopening 28 near the bottom of the accumulator. The discharge end 30 ofthe evaporator 22 is connected to pipe 32 for conducting the spentrefrigerant to the compressor 10. The refrigerant flowing throughpipe'32 is brought into heat exchange relation with at least a portionof accumulator 26 by means of a coil 36 before it reaches thecompressor.

If desired, the refrigerant in coil 36 may also be brought into heatexchange relation with capillary tube 14 as at 34 before it reaches.coil 36. The refrigerant leaving coil 36 is brought into heat exchangerelation with capillary tube 14 as at 38 to insure that no liquidrefrigerant reaches the compressor and to help cool the relatively hotliquid refrigerant issuing out of the condenser. The heat exchange at 38is conventional and will not be further referred to.

Restrictor 24, riser tube 27, and heat exchange 34 are optional and ifthey are omitted and if it is assumed that the apparatus has been out ofoperation for some time and is just being started up, the operation ofthis embodiment will be as follows:

As the liquid refrigerant flows thru capillary tube 14, the pressure isgradually decreased and flash gas is produced so that a mixture ofliquid and gaseous refrigerant is ultimately delivered at dischargepoint 18. Some of the liquid component of the refrigerant issuing out ofcapillary 14 Will flow downwardly into pipe 25 and a mixture of liquidand gaseous refrigerant will flow upwardly through pipe 19 and into theevaporator 22, The static pressure exerted by the liquid column in pipe,7,1,5 correspondingly increases the pressure drop between theaccumulator 26 and coil 36 beyond the value which would otherwisenormally prevail, and thus increases the heat exchange potential betweenthe refrigerant in the accumulator and the refrigerant in coil 36. Whenliquid refrigerant reaches coil 36, the gaseous refrigerant in theaccumulator will be more readily condensed and the resultant reductionin volume will cause liquid refrigerant to be withdrawn from pipe 25into the accumulator. In

made large enough to hold a substantial portion of the liquidrefrigerant with which the system is initially charged so that, in theabsence of gaseous refrigerant in the accumulator, it will be capable ofreceiving most, if not all, of the liquid refrigerantissuing'frorncapillary 14. Therefore, as long as liquid refrigerantflows through coil 36, or as long as the temperature of the accumulatoris at or below the saturation or condensing point of the refrigerant inthe accumulator, little, or no liquid refrigerant will flow to theevaporator through pipe '19. i

The resultant starvation of evaporator 22 will be reflected at coil 36in that, as the liquid refrigerant ebbs from coil 36 and from theevaporator, the gaseous refrigerant reaching coil 36 superheats andreverses the direction of heat flow between accumulator 26 and coil 36.Some of the liquid refrigerant in accumulator 26 is now evaporated andthe gas pressure thus generated will displace liquid refrigerant fromthe accumulator into pipes '25 and 19 to supply evaporator 22; It willbe noted that the cycle just described is not a rigid one and that it isnot carried out from start to finish according to any fixed rhythm. Inother Words, coil 36 need not be filled with liquid refrigerant nor mustthe evaporator be wholly devoid of liquid refrigerant to start or tofinish a cycle. On the contrary, as the frost point moves into, and asit recedes from coil 36, gaseous refrigerant is condensed or liquidrefrigerant is evaporated, as the case may be, correspondingly to affectthe flow of liquid refrigerant to the evaporator. This constantfluctuation, or breathing, makes the system extremely sensitive andcorrespondingly decreases the possibility of override, in eitherdirection, in the temperature of the evaporator.

The inclusion of riser tube 27 prevents the accumulation ofnon-condensing gases in the top of the accumulator the presence of whichwould adversely affect the operation of the system as first abovedescribed. For example,

whenever liquid refrigerant is evaporated in the accumulator, the gasthus formed mixes with any non-condensing gas that may be present at thetop of the accumulator and because, in the course of operation, thismixture of gases is from time to time expelled from the accumulator, thenon-condensing gases are kept in circulation where they are harmless.When used for this purpose, tube 27 may be essentially non-restrictive.In order to expel liquid refrigerant from the accumulator in response tosuperheat in coil 36, and vice versa, a measured opening 28 is in thelower portion of riser 27.

rator is at a low value with reference to the saturation temperature ofthe refrigerant in accumulator 26. It will be noted that the use ofrestrictor '24 may bring this condition about.

Since the restrictor 24 serves to intensify heat withdrawal from theaccumulator while heat exchange at 34 intensifies heat transfer to theaccumulator either may be employed separately as may be indicated.However, the combination of restrictor 24 and heat transfer at 34 servesto dampen the cycling processes and thus eliminates, or reduces,temperature override. It also provides improved flow control generally,and improved response to transient evaporator loads. For example,restrictor 24, by giving added heat transfer potential to coil 36, willrapidly condense gas in the accumulator and will prevent, or reduce theflow of liquid refrigerant to the evaporator or into suction line.Conversely, heat exchange at 34 increases the superheat of therefrigerant flowing to coil 36 and provides adequate heat transferpotential so as to initiate, or to increase, the flow of liquidrefrigerant to the evaporator. This insures an adequate supply of liquidrefrigerant to the evaporator.

For best results, and to the ends just above recited, the length of pipe32 between heat exchanger 34 and coil 36 should be kept at a minimum.

' When it is necessary to use a relatively long evaporator, it ispreferable to split it into two sections 22 and 42 as shown in Fig. 2.This merely involves connecting capillary tube 14' which leads fromcondenser 10 to the inlet end of evaporator section 42, and connectingthe outlet end 44 of evaporator section 42 to the system of Fig. 1.Except for the addition of evaporator section 42, the elements of theembodiment of Fig. 2 are identical,

in structure and in function, with the corresponding ele- The functionof opening 28 is not only to establish communication between tube 25 andthe accumulator, but also to control the rate of flow of refrigerantinto, or from, the accumulator. In other words, if, for one indicatedset of conditions, it is desired to retard the flow of liquid betweenpipe 25 and the accumulator, the size of opening 28 will be reduced, andvice versa.

The inclusion of restrictor 24 increases the pressure differentialbetween accumulator 26 and coil 36 and thus correspondingly increasesthe heat exchange potential between the accumulator and the coil.

The use of restrictor 24 is especially desirable where it is impracticalthermally to insulate the accumulator from the refrigerated medium.

Bringing the refrigerant flowing through pipe 32 into heat exchangerelation with a warm portion of capillary tube 14, as at 34 increasesthe superheat of the refrigerant before it reaches coil 36. This isimportant when the superheat of the refrigerant discharged from theevapo- 'ments of the embodiment of Fig. 1, and hence, the prime of thereference numerals used in the description of the embodiment of Fig. 1have been applied to the embodiment of Fig. 2.

When restrictor 24' is included in the embodiment of Fig. 2, evaporationsection 42 will operate at a higher pressure than evaporator section 22'and the system will be adapted to a two-temperature application. Ifrestrictor 24' is omitted, both evaporator sections will opcrate atsubstantially the same temperature.

What I claim is:

In a refrigeration system including a compressor, condenser, acapillary, an evaporator, and a suction line in a series flow path, ofrefrigerant control means comprising, an accumulator having a singlebottom opening and being in heat exchange relation with said suctionline, means defining a passageway communicating with the lower portionof said accumulator opening and with the line leading to saidevaporator, and a riser within the accumulator in fluid communicationwith the upper portion of said accumulator and connected to saidpassageway means and having an opening therein near .the bottom of saidaccumulator.

References Cited in the file of this patent UNITED STATES PATENTS2,183,346 Buchanan Dec. 12, 1939 2,291,362 Warneke July 28, 19422,423,386 Hubacker July 1, 1947 2,472,729 Sidell June 7, 1949 2,510,881Gerteis June 6, 1950 2,520,045 McGrath Aug. 22, 1950 2,740,263 KritzerApr. 3, 1956

